Abstract: A light-field multi-spectral pyrometer is designed for two-dimensional, high-temperature measurements. The proposed method is based on an unfocused light-field camera, which can simultaneously record directions and intensities of incident rays. The direction information of rays is substituted by radiation spectrums via placing an array of filters in front of the camera’s main lens, such that the image sensor can simultaneously acquire spectra and intensities of rays. For multi-spectral data processing, how to obtain the accurate target temperature under unknown spectral emissivity is a difficult problem to be solved. A multi-objective optimization method is proposed to obtain the inverse true temperature and spectral emissivity without assuming the emissivity model. In this method, the multi-objective function is established according to the radiation equations. The emissivity constraint conditions are set for the objective function, and the penalty function method is used to solve the optimization problem. The calibration experiment results of the black-body furnace show that the relative error of the light-field multi-spectral pyrometer method is less than 1%, which proves the feasibility and reliability of the proposed design and temperature inversion method.